Kim Clijsters is relishing the challenge as she plots a return to top-level tennis next year.

The former world number one caused a stir on Thursday by announcing she intends to come out retirement for a second time at the age 36.

The Belgian mother of three, who has won four grand slam titles, intends to rejoin the WTA Tour in 2020.

Clijsters, who quit the sport for a second time in 2012 due to family commitments, has revealed she has been quietly training with a view to making a comeback all year.

She claims she has nothing to prove and is doing it purely for the challenge.

"I don't feel like I need to prove anything, but I want to challenge myself and I want to be strong again," she told the WTA Insider Podcast. "This is where I'm saying 'OK, let's try this'.

"I love the challenge, I like to push myself. I'm surprised how, at times when I'm going through a rough practice, how easy it is for me to stick with it and to fight through it and to push through it.

"It's a very satisfying feeling to have that kind of challenge again."

Among the challenges is a desire to compete against the current generation of stars.

"I need to feel what it's like to stand across the net from these women," she said.

Clijsters, who has won 41 WTA titles, says she has also been inspired by the performances of other mothers in the game such as Serena Williams and Victoria Azarenka.

She said: "Mothers are trying to compete at the highest level. That is the inspiration."

Clijsters could play in the Australian Open, a tournament she won in 2011, next January. Her past achievements mean she will not have to play her way back up through lower-level tournaments as she will have unlimited access to wildcards.

Clijsters won her first grand slam at the US Open in 2005, seven years into her professional career. She retired for a first time in 2007 but returned two years later and claimed two further US Open titles as well as winning the Australian Open.

She stepped down again, apparently for good, seven years ago but now it has emerged she has been planning to return for some time. A Belgian TV company, De Mensen, have been documenting her comeback and have already filmed six months of footage.

Clijsters, however, says she will not attempt to return until she is ready.

She said: "We can talk about the start of 2020 and see where can we get a wildcard, but if I feel in December that I'm not even near to where I want to be, then I'm not going to go just for the sake of going somewhere. I want to feel like I'm getting to where I want to be."